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C. Lisse (Univ. of Maryland, Dept. Astron.), A. A. Suchkov (STScI), A. Schultz (STScI/Computer Sciences Co.)
We have identified an extensive population of young F~stars in the general direction toward the star-forming region \rho ~Oph based on the combined data from uvby and 2MASS photometry. The stars are spatially centered at a distance of 150~to~170~pc, extending over tens of parsecs in all three directions, and exhibit a moderate amount of extinction. This suggests that they are associated with the giant molecular cloud in that region, outside the cloud densest parts with which ongoing star formation is typically associated. The data indicate that many of the stars have extensive circumstellar dust disks shining in the thermal and/or scattered infrared, which implies extremely young age. For the population as a whole, young age has been inferred from the kinematics as well as position of the stars in the \log Te - MV diagram. However, the age spread in this population is probably larger than the age of the star-forming clumps in the molecular cloud. Therefore, these stars appear to trace not only the current star formation but also the star formation events that occurred sporadically throughout the cloud over a time period longer than the age of the current star-forming sites.